The estimate covers 7,742 hours that employees from the police department, Indianapolis Fire Department, Department of Homeland Security and Animal Care and Control have spent doing work associated with the Nov. 10 blast in the Richmond Hill neighborhood. Costs incurred by other city departments were not incorporated in the estimate, said Public Safety Director Troy Riggs.

The explosion is being investigated as a crime. Ten days after the explosion, law enforcement officials said they suspect gas was intentionally released into a home before a spark caused it to explode, setting off a deadly chain of blasts.

Authorities said the fumes seeped from a manipulated pipe or stove and gathered within the house, until a small spark ignited it.

It killed two people, Jennifer and Dion Longworth, who lived next door to the house where the blast occurred. Thirty-three homes are scheduled to be demolished.

Riggs said the $308,674 estimate probably is conservative.

"That just goes to show the extent of this investigation and the initial response," Riggs said.

Not only have public safety personnel been investigating the explosion site and looking for evidence, they've also been providing security.

The numbers cannot capture the pain the explosion caused to people in the neighborhood and the two lives lost, Riggs said.

"There's a lot of things that you just can't put a monetary value to," he said.

Riggs said he couldn't speculate how much longer the investigation might take.

"As the investigation continues," he said, "hopefully we'll be able to hold someone responsible."